Diabetes is a disease in which a person has high blood sugar either because the body does not produce enough insulin or because the person's cells are insensitive to the produced insulin. Accordingly, it is beneficial to monitor the person's glucose levels to identify trends in glucose levels, identify factors that affect glucose levels, evaluate foods and medications on glucose levels, and identify changes in a treatment plan.
A continuous glucose monitor (CGM) is an electronic system that measures and displays glucose level in a user's body. A CGM includes a sensor that is attached to a user's skin and held securely in place by a fastener. To measure glucose levels of the user, the sensor generally includes a metal filament that penetrates and rests in the fatty layer of the user's skin. The sensor communicates with a handheld meter that displays the glucose measurements from the sensor. A CGM is helpful to avoid potentially dangerous hyperglycemia or hypoglycemia and to help the user lower their average blood sugar levels over time.
Because the sensor is attached to the user's skin and the meter is a handheld device, wires would make the CGM difficult to use. Accordingly, CGM systems are preferably implemented with a wireless communication link between the sensor and the monitor. Accordingly, a separate transmitter may be incorporated into the sensor to transmit data to the handheld meter. Unique information must be exchanged between the transmitter and meter to create a secure communication link. Generally, for the user's convenience, the transmitter is implemented in a small form factor and includes a fixed battery that cannot be easily replaced. As such, the transmitter must be replaced when the battery is exhausted. Current CGM systems require the user to input information into the meter that identifies the transmitter, thereby allowing the meter to receive information from the sensor. This information is typically printed on the transmitter and, therefore, available for any person to read the information.
As such, the unique information can be easily obtained by observing unique information disposed on the transmitter or intercepting the communications with the unique information. Due to the importance of wireless medical devices, regulators have become interested in the security of such wireless medical devices. Further, because the user has to manually enter the unique information, replacing the transmitter is inconvenient. Moreover, battery life is an important factor in CGM sensors, and similar devices, where the battery is not designed to be replaced. Accordingly, there is a need for a method to exchange information for encrypting data in wireless medical devices that is convenient for users, and minimize battery usage.